<h1 id="chapter-1"><a class="header" href="#chapter-1">Chapter 1</a></h1>
<pre class="playground"><code class="language-rust editable">fn f() {
    println!("hello");
}</code></pre>
<pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>// Not editable.
<span class="boring">}</span></code></pre>